Not exactly... speed loss due to gravity pull and air friction would slow shell down from initial high speed...

He may have factored that in already. 900 m/sec x 2 = 1.8 km = 1.125 miles = 5940 feet, so he knocked some off for these factors. Friction is going to be the big factor, since gravity only knocks off 9.8 meters/sec.

EDIT - for grins, i calculated the altitude of the 88 based on 900 m/sec fired straight up with NO friction. You theoretically could shoot straight up at 900 m/sec, with the velocity decreasing at 9.8 m/sec, which means that the shell would come to a halt after 91.8367+ seconds. Plugging this into s = 1/2 a t^2, solving for s, gives an altitude of 41323+ meters (41.323 km, or 25.8+ miles)!!

Thanks hadn't seen this one - but I certainly have found gragantuan amounts of "interesting information" ( about flak and fuses ) ... but just like my quest for data regarding WWII TDC multi-targeting capability - no where I have looked answers the question exactly - too tactical - but then - hey tactics rule ! Unfortunately not sure historians know that !!!

Oh and btw this one is pretty much strictly about proximity fuze whereas we are looking for data on earlier "mechanical timed fuses" ... which were made obsolete by VT but not to be had by Germans ( nor my guess by Japanese ) in WWII ... fuse settings is not an issue once you get VT ( proximity ) fuses ... only on the M.T. types ...

Actually I found a site discussing setting VT fuze time less than minumum time for field artillery firing indirectly over friendlies. For AAA VT fuzes a small propeller on the rear (I think) of the shell would turn once the shell reached approx 100 mph (strange figure to find in a site concerned with ballistics) which armed the fuze after some number of turns/interval of time (which have been elusive exact figures). There was apparently a minimum effective distance. The VT fuze allowed the heavy flak to engage rapidly closing a/c. As an example, the US dive bombers at Midway came approached the KB at 16000 ft. Once they tipped over into their dives (which was just about the time they were sighted) all the heavy flak in the KB was firing mostly to feel good because the fuze setters in the mounts couldn't change the settings fast enough to account for the constantly decreasing range. The planes were in a dive for say 45 secs figuring roughly 200 kt dive speed. That amount of time would have allowed a 5"/38 with a decent gun crew to crank out 12-15 VT rounds that automatically exploded at whatever range the target was at. A quantum jump in the amount of lead between the would be bombers and their targets.

No question that proximity fuses were quantum leap ... and there is a whole lot more data about them out there than for the older M.T. fuses ... thing is we would like to have data on M.T. fuses to really nail our issue ... your speculation ( which is certainly plausible ) is that VT minimum might be the same as M.T. minimum or at least close ... but I'm still gonna keep looking for direct data on M.T. since I know germans only had M.T. during the war ... they never got VT .. and I presume that Japanese also never got VT though I don't have definitive data on that ( yet ) either.

BTW at least some M.T fuses may have worked on a different principle than the propeller system you describe.

The US M.T. M43A5 fuse which was used on the US Army AA rounds for 3in, 90mm and 105mm had an activation system described as:

"The mechanical time fuze, M43A5 used in this shell is driven by a pair of weights which are acted upon by the centrifugal force set up by the rotation of the shell in flight. The time ring is graduated for 30 seconds maximum setting" source: US Army Catalog of Standard Ordnance, 1944 as reproduced in Greenhill Books Edition, 2001 introduction by Ian V. Hogg

Further in this same reference, there is mention of an advanced mount ( M2 ) for the 90mm AA gun which also had an automated rammer-fuze setter ... described as follows:

"The purpose of the combination fuze setter rammer, which is operated automatically and is controlled by a director through remote control, is to shorten and hold constant the time interval between setting a time fuze and firing the round ... "

Note that even in the Army I was in ( late 70s ) .. field artillery fire procedure had FDC ( Fire Direction Center ) send deflection, elevation and round, charge and fuze setting over radio telephone ... which then had to be repeated by radio telephone operator and then executed by gun crew ... all this taking best case a number of seconds 10-20 depending on the order ... an early WWII AA system could not have been much different and AA directors in most services did control mutliple guns which were too far apart to hear orders from a single person ... hence this automated rammer-fuze setter would have been a big step forward ( Germans had something similar on their 105mm flak weapon ). The "gap" between the director determining the fuse setting and the elevation and the deflection for each gun ... and the rounds being fired ... might have been as short as 5 seconds depending on how the data was relayed and which functions could be performed in parallel ... but this gap could not have been zero ... and whatever it was .. it would have to be factored into the director data as the target would be in a different place after these seconds had passed by ... so the problem was not only estimating where the target would be during the flight time of the round .. but also during the time between when the direcctor data was calculated and when the round was fired.

The auto-mated rammer fuse setter briefly made this problem simpler by reducing the time ( and hence the error ) and making the time more consistent ) not done by humans ... of course the VT fuze put all the arcarne stuff out of business .. and after the war ... everyone converted over to VT .. and that is where we are today ( for the most part ! )

But despite all this interesting stuff ... I still don't have direct data on minimum effective range of heavy AA and that is really the question I'm trying to address ...

The short version is that the maximum fuze settings are 30 seconds ( is that what the 30 means ? ) whereas the minimum settings vary from version to version ... from 1 second to 2 seconds ... hence going back to Apollo11's blrub above where he says 88 minimum fusing was 2-3 seconds .. well he was pretty close ... this data pegs it at 1-2 seconds depending on exactly which flavor of fuse was in use by that battery on the day in question ! All of these fuses were centrifugal weight driven.

Oh and this fuse data is on pages 278-279 of Hogg, Ian V. "German Artillery of World War II", Greenhill Books, London, 1997

Now this being said - does this enable us to "calculate" the exact minimum effective altitude of ( at least 88mm ) heavy flak ?

Well maybe.

The more I've thought about this, the more I think it might be more complex than we think. The minimum fuse setting does certainly put a lower bound on things. However, the process of calculating the director data ( gun deflection, elevation, fuze setting ) and transmitting this data to the gun and having the gun crew execute ( which includes traversing the weapon to the ordered deflection and elevation, setting the fuse, loading the round ) and fire the round and the round fly to the spot where the fuse sets it off ... all this takes X seconds ... in the mean time the target aircraft .. moved to position "P" ... the problem for the director was to estimate where position "P" would be at the time the projectile got there .. based on how long all that other stuff was expected to take to happen.

Because for the most part ( in most services ) this process was not completely automated ( i.e. humans were involved in executing some of the process ) .. the longer it took ... the more likely errors were introduced .. and the more likely the target plane would not be exactly at the position predicted ( and hence the greater likelihood a miss would result ! )

Hence due to the greater apparent different in deflection and elevation for low flying targets ( they - on average - move farther across the "aiming canvass" than targets at 20,000 feet in the same number of seconds ) the minimum effective range may be as much as matter of doctrine specifying at what altitudes we will fire under what conditions. In conjunction with of course the hard parameters like minimum fuse setting.

Thus my "hypothesis" is that even above the minimum fuze setting altitude .. that heavy AA battery's would have had a lower frequency of hits until the altitude was high enough to reduce the "tracking problem" to one which could be dealt with by the predicting technology.

So I've now shifted my search into "doctrine - and I do have a new source on that ... book by Westermann "FLAK - German Anti-Aircraft Defenses, 1914-1945, University Press of Kansas, 2001" ... so I'll take a look at that and speak up if it helps. Oh and "doctrine" will also address the willingness and pros and cons of firing "barage" fire ( or unaimed fire ) as this certainly could be done - but has the downside of expended large quantities of ammunition. So under what conditions was this used and to what effect ?

The short version is that the maximum fuze settings are 30 seconds ( is that what the 30 means ? ) whereas the minimum settings vary from version to version ... from 1 second to 2 seconds ... hence going back to Apollo11's blrub above where he says 88 minimum fusing was 2-3 seconds .. well he was pretty close ... this data pegs it at 1-2 seconds depending on exactly which flavor of fuse was in use by that battery on the day in question ! All of these fuses were centrifugal weight driven.

Oh and this fuse data is on pages 278-279 of Hogg, Ian V. "German Artillery of World War II", Greenhill Books, London, 1997

Now this being said - does this enable us to "calculate" the exact minimum effective altitude of ( at least 88mm ) heavy flak ?

Well maybe.

The more I've thought about this, the more I think it might be more complex than we think. The minimum fuse setting does certainly put a lower bound on things. However, the process of calculating the director data ( gun deflection, elevation, fuze setting ) and transmitting this data to the gun and having the gun crew execute ( which includes traversing the weapon to the ordered deflection and elevation, setting the fuse, loading the round ) and fire the round and the round fly to the spot where the fuse sets it off ... all this takes X seconds ... in the mean time the target aircraft .. moved to position "P" ... the problem for the director was to estimate where position "P" would be at the time the projectile got there .. based on how long all that other stuff was expected to take to happen.

Because for the most part ( in most services ) this process was not completely automated ( i.e. humans were involved in executing some of the process ) .. the longer it took ... the more likely errors were introduced .. and the more likely the target plane would not be exactly at the position predicted ( and hence the greater likelihood a miss would result ! )

Hence due to the greater apparent different in deflection and elevation for low flying targets ( they - on average - move farther across the "aiming canvass" than targets at 20,000 feet in the same number of seconds ) the minimum effective range may be as much as matter of doctrine specifying at what altitudes we will fire under what conditions. In conjunction with of course the hard parameters like minimum fuse setting.

Thus my "hypothesis" is that even above the minimum fuze setting altitude .. that heavy AA battery's would have had a lower frequency of hits until the altitude was high enough to reduce the "tracking problem" to one which could be dealt with by the predicting technology.

So I've now shifted my search into "doctrine - and I do have a new source on that ... book by Westermann "FLAK - German Anti-Aircraft Defenses, 1914-1945, University Press of Kansas, 2001" ... so I'll take a look at that and speak up if it helps. Oh and "doctrine" will also address the willingness and pros and cons of firing "barage" fire ( or unaimed fire ) as this certainly could be done - but has the downside of expended large quantities of ammunition. So under what conditions was this used and to what effect ?

Nice find - thanks!

BTW, please note that only few heavy AA batteries (German that is) were trained and equipped to track and shoot individual (or groups) targets. Those were usually "Wurzburg" radar coupled batteries.

Other batteries used good old reliable system of placing as many shells as fast as possible in selected space of sky whilst incoming enemy bombers would just fly into this "barrage" or "curtain"...

EDIT - for grins, i calculated the altitude of the 88 based on 900 m/sec fired straight up with NO friction. You theoretically could shoot straight up at 900 m/sec, with the velocity decreasing at 9.8 m/sec, which means that the shell would come to a halt after 91.8367+ seconds. Plugging this into s = 1/2 a t^2, solving for s, gives an altitude of 41323+ meters (41.323 km, or 25.8+ miles)!!

BTW, the actual MAX altitude was around 10000m (10km)

Mass of shell (also known factor) is needed in much more complex calculation when air resistance is used...

Some years ago I read a book called The Deadly Fuze by Ralph Baldwin, that went into considerable detail on the devolpment of the VT fuze. As a former user I can testify to the advantages of this system. While it does have the capacity to vary the range gate on the fuze most of the time, in naval use anyway, it is employed "right out of the box". This makes firing a lot quicker. The MT type fuze requires the individual round to be inserted in a fuze cutter, a cylindrical device on the gun mount, connected to the fire control computer which rotates the timer bands on the MTF to the correct configuration before loading. MTF can be set manually, via a special wrench, but that tends to be really slow. The MT fuze is most commonly encountered in star shells these days, although it can be used with just about any shell type (the fuze well dimensions and threading are pretty much universal in USN ammunition above the machine gun, defined as 40mm or less in USN parlance, size weapons). Someone mentioned point and train as a problem for AAA. Even in WWII this was becoming a problem and led the USN to abandon the 40mm for the hydraulically driven 3" mount which has a much faster rate of train, which itelf was supplanted by various point defense systems due to the vast incrrease in angle change that came with jets. It would be interesting also to determine what system of fire control that Japan used for AAA. From sources such as Principles of Naval Orndnance and Gunnery the US systems became increasingly computer controlled and cooordinated through the war which should lead to a progressive increase in their effectiveness, especially coupled with the VT rounds. I don't have a great knowledge of WWII Japanese TO&E and am curious about their AAA/ADA organisation. If it is as weak as it sounds (I have, sofar only played to April, 1942 and that against the AI) is this historical? I don't recall reading much where the Japanese flak aroused the respect in allied fliers that the German system had. Should this be the case was it a question of technology, doctrine, training or production limitations. Doctrine and training could be dealt with, although probably slowly given the way naval air training reacted during the war, but technology or production only at the expense of something else.

It would be interesting also to determine what system of fire control that Japan used for AAA.

That was their weak point. Most Japanese AAA guns onboard ship were under local control without radar direction. They normally used the gun captain to pick out the target with a pointer. The net effect was to have a fairly large volume of fire late in the war but it was pretty ineffective compared to the US and Brits. Yamato put up a very heavy AA fire but it was uncoordinated and ineffective. The Beehive shells fired from the 18' were only effective at long range and little effect during her last battle.

While some of the Japanese later radars were pretty good, they were underpowered and their integration into the fire control solution left a lot to be desired, nowhere near the degree of integration of US systems.

As far as ground based AAA goes, the Japanese were far behind the Germans in flak effectiveness. Their guns were good enough but without a decent fuze system and an inability to accurately judge the target's height, they just could get enough lead close enough to the target. In the early years, the Germans would sometimes send up an aircraft to pace the bombers reporting of their speed, altitude and course. The Japanese never tried the same.

More useful data – there is soooo much … that I will first provide a summary and then drill into details based on any questions or comments.

Eventually I will write the whole thing up and post on the Uber WITP Wiki …

Ok first, we are trying to address whether there was a “flak gap” somewhere between 6,000 to 9,000 feet in the Japanese WWII AA. As per the original post there seems to be one in the game.

So far I have found three pieces of evidence for the existence of some kind of flak gap in WWII AA.

(1) LeMay’s rational for the low altitude fire bombing based in part on his “hunch” that the Japanese flak would not be effective in this altitude band ( sources mentioned above in post #22 ) (2) Ian Hogg’s statement that Germans were first to recognize the “flak gap” between light and heavy AA ( source mentioned above in post #26 ) (3) Westermann’s repeated statements that Germans placed the barrage balloons between 6,000 and 9,000 feet in one band … and below 3,000 feet in the other band. This split deployment would only make sense if something was going to fire into the 3,000-6,000 foot gap and something was going to fire over 9,000 feet. The two devices available were light flak and heavy flak … unfortunately Westermannn stops short of telling us why this 3,000 foot gap in the Balloon deployment exists – but until I find something to the contrary I will think that we are seeing the “shadow” of the flak gap – with the balloons deployed from 6,000 to 9,000 feet.

As early as 1917 the Germans recognized that “barrier fire” was inefficient and wasteful and that an effective method of “directed fire” was essential ( ibid. p22 )

Before the end of the war ( WWI ), the Germans introduced an early 88mm purpose built flak weapon with a timed fuse. Although an improvement, the timed fuse had to be set manually and the guns crew now needed to compensate for both the time required to set the fuse and the time required to aim the gun at the predicted location of the target aircraft. The length of these delays depended upon individual gun crew proficiency ( ibid. p23 )

By 1935, the newer 88s added direct transmission of firing solution data from the director to the gun. Known as Ubertrangungs 30 this device sent elevation and traversal ( a.k.a. deflection ) data to the gun whereupon a panel of lights lit up which the gunner then had to “match” by traversing the gun into the indicated position. A later ( 1939 ) version Ubertrangungs 37 – had a double system of dials and the solution was transmitted electronically to these dials and the gunner the matched ( the other set of dials ). This system apparently only provided elevation and deflection , not fuse settings so these would have been passed by other means. ( Hogg, GERMAN ARTILLERY OF WWII, p163-164 )

The below summary is all from Westermann.

In 1940 the very high availability of flak ammunition lead to a general relaxation on “barrier fire” and for this year alone, barrier fire came into general use. Also the rapid expansion of the flak arm upon the start of the war left many battery’s without director equipment hence “barrier fire” ( un-aimed fire ) was the only viable option. In Dec 40 the shoot down totals were 24 planes by directed fire and 1 plane by barrier fire, thus illustrating the greater efficiency of directed fire during the “barrier fire” era.

In early 1941 orders were issued against barrier fire as directors became much more generally available and flak ammunition shortages were now happening. For the rest of the war, barrier fire was generally only allowed for “foreign” weapons ( captured equipment ) which were usually manned by less well trained men and were usually without directors.

In early 1944 for example of the roughly 2,000 batteries defending the Reich, about 200 were “barrier fire” enabled .. with 124 of these being equipped with Russian AA gear.

Shortages of directors continued throughout the war, though in the second half of the war, rather than expand inefficient barrier fire to the regular batteries, these were grouped into “super-batteries” of up to 24 guns ( thus requiring less directors )

In 1944 a new type of director, the Zug 44 was produced which could control up to 32 batteries !!! However, no data on field use of this device is yet available.

An interesting but mostly unrelated piece of data is that in 1943 116,000 young women were drafted into the Flak Arm as search light battery “troops” … there was a lot of debate about this but even Hitler agreed to it.

The 105mm AA gun however, had a “match the dials” system probably similar to the U35/37 described above. It is also stated that fuse setting is automatic though details of how this is done are not provided.

Summary ( of summary )

Evidence suggests that there was probably flak gap in all AA services of somewhere between 5,000 and 10,000 feet due to the inability of light flak to effectively fire into this band and the inability of the heavy flak to effectively fire into this band. Light flak had a greater tracking problem to solve at this altitude and generally had less sophisticated director equipment to assist in the solution. Heavy flak also had a tracking problem but this was exacerbated by greater time requirements to set fuses and lay the gun. The Japanese gap may have been a bit worse that the German gap due to even less sophistication on the Japanese equipment in general.

It is probably that later low level B29 attacks ( after Okinawa ) such as the May 25th Tokyo raid, did run into “barrier fire” though the Japanese were clearly deploying and using directed fire for their heavy artillery.

So – certainly no 100% definitive answers – but the above is a summary of what I’ve seen in the past couple of days. The subject is intriguing to me probably for 2 reasons … one I was in Field Artillery which is at least a distance sister service so discussions of fusing and laying a gun are familiar – and the other is the difficulty of finding data on the mechanical fuse era of AA weapons ( 1917 – 1943 ).

In the official USAAF training film "Flak" (1944), dealing with both German and Jap flak, the existence of a flak gap was referred to as a "legend", and stated that all heavy flak has a minimum effective altitude of about 3000 feet. It also stated that flying at extremely low altitude was safer than flying at low altitude because of aiming problems.

We have to consider all data - and it is not unusual when digging into details - to find conflicting data - hence we must look far and wide - and when the day is done - assimilate all the data and see if we can determine the truth. Sometimes we can - sometimes we have to decide we just can't be sure.

For example, the film spends most of its time talking about evasive manuvers - whereas LeMay felt that 8AF bombing accuracy was heavily ( and negatively ) influenced by evasive manuvering ... p289 Westermann, op cit ( per above posts ).

Also the film indicates heavy flak is effective at 3,000 feet because that is the altitude at which the fuse becomes effective - however it could be that lag time between ability to transmit targeting data and then set the fuse and lay the gun would significantly reduce chance of hit for "lower tech" flak systems - relying on less automation in the process - as the Japanese had. So I wouldn't on maximum effectiveness at the lowest altitude where the fuse becomes effective - that is just the first altitude where any result is possible.

And here is a Master's thesis which states they LeMay believed that Japanese Home Island Low Altitude flak was ineffective and that this was one of the reasons for the shift to low altitude bombing ( though many others are given as well ) ... P69 of the following link.

And here is a Master's thesis which states they LeMay believed that Japanese Home Island Low Altitude flak was ineffective and that this was one of the reasons for the shift to low altitude bombing ( though many others are given as well ) ... P69 of the following link.

Only problem is that these are almost at the altitudes that I would think were most optimal for flak ... ( 12,000 to 20,000 ) .. so maybe all this means is that Japanese flak sucked period ! The above strikes were all "after" the Okinawa interlude ... so late May on .... but they are above any "gap" whether it existed or not ( I would think ).

This includes Army units only ( not Navy ) but we have to start somewhere ... and this does not include numerous "machine cannon" units which were only light flak ( nor the light flak components of the above listed units ) and I haven't seen seen data on production figures for either 75mm AA or 105mm AA ... and last but not least, the above units have relatively few "dates" associated with them .. but certainly the OB was not static throughout the war ... some units were disbanded and some were first created ... I have of that data .. but doubtly all of it.

Source: Underwood ( reprinting Madej, "Japanese Armed Forces, Order of Battle, 1937-1945 ( 2 vols ), Game Publising Company, Allentown PA 1981 )(Note that essentially Madej just reprints documents from the US archives which are either caputed enemy records and or records produced by the military during or shortly after the war )

( gee the above is a direct quote - but more un-said than said ) .. I'd guess these had best case 8 x 75mm ... and that maybe 20-33% of them at most would be in home is ... but that is pure guess based roughly on the Army breakdown

So guess here would be no more than 4 x 75mm per unit ... with maybe 33 to 66 % of them in home is

============= Army Replacement Units ( 3 types )

Type 1 had 8 x 75mm Type 2 had 6 x 75mm Type 3 had 4 x 75mm

Assume 6 of the 7 of these would be in home islands - so on avg probably 36 more guns from these

=============

205 x .28 x 8 = 459 007 x 4 = 028 036

Total 523

============= So combined total adding in Naval and replacement units is now

0468 0523 ----- 0991

============= As to the Tokyo raid, I assume you mean the May25, 1945 attack. Per pages 638-9 of volume 5 of the Blue Books, 502 B29s bomb ... altitude not given, but altitude for Tokyo attack 2 days prior by 562 B29 was 7,800 to 15,100 so assume same. Total 26 B29 destroyed all causes, 100 damaged all causes, percent hit by flak unknown assume at about 50% based on similar ratio in Europe ( 50% of British Bomber losses were due to enemy flak or fighters ).

BTW losses from the Tokyo raid 2 days prior were 17 lost to all causes ( of which 4 of these were lost to operational causes ) out of 562 attacking B29s ( p638 v5 Blue Books )

How many guns at Tokyo that night ? Wouldn't even wanna hazard a guess without more data ... I have a few units pegged to Tokyo .. but a lot of them are just "Japan" ...

So will there be a change with the coming patches or is it just a new Allied advantage we all know now? To attack always at 6000 feet with everything because Allied know that Japanese flak doesn´t even shoot at them. Japanese can´t do that because with the crappy planes they have they get shot down by light flak as easily at low alt like at higher alt with heavy flak. grrrrrrrrrrrrrrrrrrrrrrr

As it stands right now all you IJN fanboys should just count your blessings that your planes don't get shot at with VT-fuzed shells. BTW, there has been some doubt expressed as to whether the Japanese IJN/IJA developed this technology into an operational weapon. THEY DIDN'T!!!!

As a proof I would suggest that all increases in AA power result from an 'upgrade' requiring the ship to put in to a shipyard. Taking on a load of ammo for ones guns does not require a "yard period" to repair the sys damage.

Conversion to VT-fuzed ammo would essentially have to appear as a spontaneous increase in the flak value of every ship armed with 5"/38 cal guns on a certain date. Pretty sure nobody has seen anything of the sort.

But note that use of VT aboard ships was not 100% from a given date forward for the rest of the war. Restrictions were placed on use of VT fuses in areas where they could possibly fall ashore and be recovered / examined by the enemy .. which is why you can see pictures of ships using MT fuses even at Okinawa. But certainly not sure how to model that within the current system. Modeling VT in general would be possible with another device type ( though we are totally out of device types in CHS ). So one change we need to advocate for going forward is to expand the size of the device array.